Don't include padding in writingPtr length

We were passing the full record size rather than the amount we actually
intended to write. This was wasteful both for rollback preimages as well as
needlessly bloating the journal.
Make DiskLoc trivially copyable and movable

Writing explicit copy operations causes worse codegen. Among other things, it
prevents passing DiskLocs in registers.
Use OwnedPointerVector to track Changes

Saves one new/delete pair per change registration.
SERVER-16164 Optimize table scans on wiredtiger
SERVER-16195 Clean up createCollection shell helper to support noPadding
SERVER-16199 Use WT bulk cursor for bulk index builds